Xerostomia, also referred to as Dry Mouth, is a chronic condition due to an inadequacy of saliva flow in the mouth. It in itself is not a disease but is a symptom associated with a wide variety of causes and conditions.
There are many causes of xerostomia, including the use of medications such as antihistamines, antidepressants, anticholinergics, anorexiants, antihypertensives, antipsychotics, anti-Parkinson agents, diuretics, sedatives, antiemetics, antianxiety agents, decongestants, analgesics, antidiarrheals, bronchodilators and skeletal muscle relaxants.
Another cause of xerostomia is as a secondary effect of a disease. The most common disease causing xerostomia is Sjögren's syndrome, a chronic inflammatory autoimmune disease. Chronic inflammatory diseases, such as sarcoidosis and amyloidosis, are also causes of xerostomia.
Systemic diseases that can cause xerostomia include rheumatoid arthritis, systemic lupus erythematosus, scleroderma, diabetes mellitus, hypertension, cystic fibrosis, bone marrow transplantation, endocrine disorders, nutritional deficiencies, nephritis, thyroid dysfunction, and neurological diseases such as Bell's palsy and cerebral palsy. Hyposecretory conditions, such as primary biliary cirrhosis, atrophic gastritis and pancreatic insufficiency, may also cause xerostomia.
Dehydration resulting from impaired water intake, emesis, diarrhea or polyuria can result in xerostomia. Psychogenic causes, such as depression, anxiety, stress or fear, can also result in xerostomia. Alzheimer's disease or stroke may alter the ability to perceive oral sensations. Dry mouth is often exacerbated by activities such as hyperventilation, breathing through the mouth, smoking, or drinking alcohol. Trauma to the head and neck area can damage the nerves supplying sensation to the mouth, impairing the normal function of the salivary glands. Additionally, xerostomia is the most common toxicity associated with radiation therapy to the head and neck.
Although xerostomia occurs in people of all ages, it is an especially common complaint in elderly people, and is estimated to affect approximately twenty percent of the elderly. In people suffering from xerostomia, common complaints secondary to the xerostomia include oral dryness when eating, the need to sip liquids in order to swallow dry foods, difficulty swallowing, and the perception of a dry mouth due to too little saliva.
Xerostomia is also responsible for secondary effects, including an increased incidence of dental caries and demineralization of teeth, and increased risk of secondary infections such as candidiasis. Therefore, ancillary treatment for xerostomia often includes the use of fluoride therapy for caries control and antifungal medications such as nystatin.
For the treatment of xerostomia itself, artificial saliva or saliva substitutes can be used to replace moisture and lubricate the mouth. These substitutes are available in a variety of formulations including solutions, sprays, gels and lozenges. These artificial saliva substitutes may contain an agent to increase viscosity, such as carboxymethylcellulose or hydroxyethylcellulose, minerals such as calcium and phosphate ions and fluoride, preservatives, and flavoring agents.
The most commonly utilized oral treatment for xerostomia is BIOTENE® (GlaxoSmithKline plc, United Kingdom). BIOTENE® is available in oral rinse and spray formulations, as well as an oral gel formulation. All formulations of BIOTENE® contain water glycerin, xylitol, and a mucoadhesive polymer. The BIOTENE® gel formulation additionally contains a carbomer as a thickening agent, in addition to its mucoadhesive properties. The sugar alcohols xylitol and sorbitol are present in the BIOTENE® formulations in small amounts in order to provide sweetness.
Kawa, U.S. Patent Application No. 2008/0317703 discloses an oral care product for xerostomia which contains a combination of polyvinyl pyrrolidone (PVP) or a vinyl pyrrolidone/vinyl acetate or vinyl alcohol copolymer in combination with an anionic mucoadhesive polymer. Kawa discloses that the anionic polymer has an affinity for mucous membranes of the oral cavity and provides good mouth coating. However, such polymers often are overly tacky and, therefore, have negative sensory characteristics. The combination of the PVP or copolymer with the mucoadhesive polymer overcomes the bad mouth feel of the composition due to the presence of the mucoadhesive polymer.
Kawa further discloses that the composition may contain additional excipients, one of which may be a humectant. If present, the humectant may be glycerin, sorbitol, xylitol, propylene glycol, polyethylene glycol, or a combination.
Soderling et al, Curr. Microbial., 56:382-385 (2008), discloses that xylitol inhibits the growth of Streptococcus mutans, an organism that is commonly found in the oral cavity and which is a significant contributor to the development of dental caries.
In 2012, Ashland Inc. (Covington, Ky.) announced the release of LUBRAJEL® BA for the treatment of dry mouth. LUBRAJEL® BA hydrogel is a clathrate of glycerin and polyacrylate that encloses water molecules via hydrogen bonding and Van der Waals forces. Because it binds water and is a highly viscous gel, LUBRAJEL® BA was marketed as an ingredient to provide moisture to the mouth. Ashland further disclosed that formulations containing LUBRAJEL® BA perform similarly to saliva under varying oral conditions. Moreover, these formulations had better mucoadhesion than saliva, so that it is expected that, with formulations containing LUBRAJEL® BA, the mouth will maintain longer hydration and relief from dry mouth (xerostomia).
A significant need exists for an oral care product that contains xylitol at a concentration sufficiently high to inhibit the growth of S. mutans and which product maintains the concentration of xylitol in the mouth, and particular on the oral mucosa, for a time sufficient for the xylitol to inhibit the growth of S. mutans in the mouth.